A reliable automatic tension control system for a continuous belt conveyor and its control method

Abstract

The present invention discloses a reliable automatic tension control system for a continuous belt conveyor and its control method, which solves the problems existing in the existing belt conveyor tensioning technology, such as vehicle slipping, belt breakage, and unstable tensioning. The present invention includes a main winch motor provided on a tensioning winch, a wire rope reel is arranged in transmission cooperation with the main winch motor, a tensioning wire rope cooperating with a tensioning frame is wound on the wire rope reel, a tension sensor is arranged on the tensioning wire rope, both the main winch motor and the tension sensor are connected to a control unit, a brake is arranged on the drive shaft of the main winch motor, a brake motor for driving the opening and closing is arranged on the brake, and the brake motor is connected to the control unit through a brake relay. The control unit is connected with a frequency converter, a resistance box is arranged in cooperation with the frequency converter, the main winch motor is connected to the control unit of the frequency converter, and a rotary encoder is also connected between the main winch motor and the control unit. The control of the present invention is simple, the cost is low, and the operation is stable and reliable.

Description

Technical Field

[0001] The invention relates to the technical field of automatic tensioning of continuous belt conveyors, and in particular to a reliable automatic tensioning control system for continuous belt conveyors and a control method thereof. Background Art

[0002] With the vigorous development of China's shield industry, the application of hard rock tunnel boring machines (TBMs) is also increasing. As a slag discharge device for TBMs, continuous belt conveyors are an indispensable component. During the TBM excavation process, the continuous belt conveyor can continue to extend with the advancement of the TBM main machine to achieve the purpose of continuous slag discharge. There are generally two types of automatic tensioning devices: heavy hammer automatic tensioning and variable frequency automatic tensioning. The variable frequency automatic tensioning system is relatively complex, generally including tensioning winch, brake, wire rope drum, inverter, controller, human-machine interface, etc.

[0003] Generally, variable frequency automatic tensioning is divided into two types: an automatic tensioning system with continuous motor operation and an automatic tensioning system with intermittent motor operation. The automatic tensioning system with continuous motor operation balances the tension of the belt conveyor by giving the belt conveyor a continuous dynamic force through continuous operation of the motor, thereby achieving a dynamic equilibrium state. This mode has a good dynamic response speed and is a closed-loop control mode. It is necessary to add an encoder to the motor to achieve a closed-loop control. For example, the automatic tensioning system of the continuous belt conveyor for the yellow and loose belt conveyor is of this mode. The automatic tensioning system with intermittent motor operation means that the motor will only work when there is a deviation between the actual value and the set value. When there is no deviation, the brake holds the motor tightly, and the motor and winch are in a stationary state. Compared with the two, the automatic tensioning system with intermittent motor operation is easier to control, more reliable, and more energy-saving and environmentally friendly.

[0004] After searching, the utility model patent with application date of 2016.06.13 and application number CN205675691U discloses a permanent magnet motor variable frequency tensioning device, including a tensioning winch; the tensioning winch is provided with a winding wheel and a driving mechanism for driving the winding wheel to rotate, a rope is wound on the winding wheel; a tension sensor for sensing the rope tension is provided on the rope; the winding wheel is connected to the permanent magnet motor through a reducer; the frequency converter is electrically connected to the permanent magnet motor, the brake and the tension sensor respectively, the frequency converter is used to control the rotation direction and start and stop of the permanent magnet motor, and to brake the transmission mechanism between the permanent magnet motor and the reducer by controlling the brake; it is also used to receive the rope tension sensed by the tension sensor, and according to the rope tension sensed by the tension sensor, control the operation of the permanent magnet motor and adjust the rope tension. The above technical solution mainly solves the problems of poor long-distance application effect and slow dynamic response speed of the variable frequency automatic tensioning device.

[0005] In addition, there is a utility model patent with an application date of July 7, 2015 and an application number of CN204945745U, which discloses a mine-used variable-frequency tensioning winch control system. The power supply of this technical solution is connected to the winch variable-frequency motor through an explosion-proof filter reactor and an explosion-proof frequency converter. The winch variable-frequency motor is connected to the winch transmission device through a hydraulic brake. The winch transmission device is connected to the tensioning trolley through a tensioning drum. The explosion-proof frequency converter is controlled by an explosion-proof PLC control box. The explosion-proof PLC control box is bidirectionally connected to a centralized control center. The explosion-proof PLC control box is connected to control a hydraulic brake, a speed sensor, a tension sensor, and a pressure transmitter. This technical solution provides an electrical control design idea for an explosion-proof variable-frequency automatic tensioning device.

[0006] The technical solutions of the above two utility model patents have solved the problem of belt tensioning. However, with the development of technology, the above two technical solutions have both shown deficiencies, lacking reliability in aspects such as mechanical cooperation and electrical control, and both have technical problems of high use cost and poor stability. Summary of the Invention

[0007] In view of the deficiencies in the above background technology, the present invention proposes a reliable automatic tensioning control system for a continuous belt conveyor and its control method, which solves the technical problems of high use cost and poor stability of the existing automatic tensioning system for continuous belt conveyors.

[0008] The technical solution of the present invention is realized as follows: A reliable automatic tensioning control system for a continuous belt conveyor includes a tensioning winch. A main winch motor is provided on the tensioning winch. A wire rope drum is arranged in transmission cooperation with the main winch motor. A tensioning wire rope that cooperates with the tensioning frame of the continuous belt conveyor is wound on the wire rope drum. A tension sensor is provided on the tensioning wire rope. Both the main winch motor and the tension sensor are connected to a control unit. A brake is provided on the drive shaft of the main winch motor. A brake motor for driving the opening and closing is provided on the brake. The brake motor is connected to the control unit through a brake relay. A speed reducer is arranged between the drive shaft of the main winch motor and the wire rope drum. The control unit includes a PLC slave station. The tension sensor and the brake relay are both connected to the PLC slave station. The PLC slave station is connected to a frequency converter. A resistor box is arranged between the main winch motor and the frequency converter. The main winch motor is connected to the PLC slave station through the frequency converter. A rotary encoder is provided on the main winch motor. The rotary encoder is connected to the PLC slave station.

[0009] During the belt tightening (loosening) process, there is always a large tension, so it is very important to prevent the vehicle from slipping during the start and stop process. During the operation of the continuous belt conveyor, the main hoist motor will be in a low-speed and high-torque state for a long time. Therefore, the frequency converter is preferably a heavy-duty frequency converter of the Schneider ATV71 series. This frequency converter can achieve zero-speed full torque in the closed-loop mode, and this feature can greatly reduce the vehicle slipping phenomenon. In addition, the belt tightening (loosening) process of the continuous belt is similar to the lifting (lowering) process of a crane. Combining the control of the brake by the lifting mode of the frequency converter can achieve no vehicle slipping at all. In addition, when loosening the belt, the main hoist motor will be in a power generation state under the traction of the belt tension, especially during the final tunneling period when the belt is long, and this phenomenon will be more obvious. Therefore, in this design, a resistor box matching the frequency converter is configured to consume the excessive energy on the bus, and it also plays a certain braking role.

[0010] Furthermore, at least two tension sensors are provided, and each tension sensor is a temperature-compensated tension sensor. Since the tension sensors are under the action of alternating stress for a long time, the probability of failure is increased. Therefore, two sensors are used for redundancy to reduce the probability of equipment shutdown. Since the climates of tunnel construction sites are different, the weather is cold in winter, and the lower temperature will have a greater impact on the tension sensors, resulting in a decrease in control accuracy. The temperature-compensated tension sensors are adopted to ensure the accuracy of the signal output of the tension sensors when the temperature changes greatly. Even after the tension sensor fails, the current tension value can be judged regularly through the zero-speed full-torque characteristic of the frequency converter, and it can be roughly compared with the tension set value to perform the belt loosening (tightening) action, and then alarm to the upper computer and wait for maintenance.

[0011] Furthermore, the tensioning frame includes a belt turning frame. A first group of belt turning cylinders is arranged on the belt turning frame. A belt tensioning vehicle is arranged opposite to the belt turning frame. A second group of belt turning cylinders corresponding to the first group of belt turning cylinders is arranged on the belt tensioning vehicle. The belt of the continuous belt conveyor is wound between the first group of belt turning cylinders and the second group of belt turning cylinders. One end of the tensioning steel wire rope is fixed on the belt tensioning vehicle.

[0012] Furthermore, the belt tensioning vehicle includes a tensioning vehicle fixed support. A tensioning vehicle walking support is slidably arranged on the tensioning vehicle fixed support. The second group of belt turning cylinders is arranged on the tensioning vehicle walking support.

[0013] Furthermore, rollers are arranged below the tensioning vehicle walking support, and guide rails matched with the rollers are arranged above the tensioning vehicle fixed support, effectively enhancing the convenience of tightening and loosening the continuous belt.

[0014] Further, the tension winch includes a winch bracket for fixing the main winch motor and a fixed pulley bracket corresponding to the traveling frame of the tension vehicle. A first fixed pulley group is arranged on the fixed pulley bracket, and a second fixed pulley group corresponding to the first fixed pulley group is arranged on the traveling bracket of the tension vehicle. The tension steel wire rope is wound back and forth between the first fixed pulley group and the second fixed pulley group, and multiple strands of the tension steel wire rope are connected in parallel between the first fixed pulley group and the second fixed pulley group, fully ensuring the reliability of traction.

[0015] Further, a steel wire rope reversing frame is arranged between the fixed pulley bracket and the winch bracket. A reversing fixed pulley is arranged on the steel wire rope reversing frame. The tension steel wire rope passes through the reversing fixed pulley and the first fixed pulley group in sequence from the steel wire rope reel and is connected to the second fixed pulley group, so that the arrangement position of the tension steel wire rope can be adjusted conveniently.

[0016] A control method for a reliable automatic tension control system of a continuous belt conveyor includes a tension control process, a parking control process, and a belt loosening control process. The slave PLC is connected to a control panel, and a set tension value, a brake release current value, and a brake closing current value are input into the slave PLC through the control panel. The tension control process includes:

[0017] When the tension detected by the tension sensor received by the slave PLC is less than the lower limit of the set tension value, the slave PLC controls the frequency converter to work. The slave PLC outputs exciting current to pre-excite the main winch motor through the frequency converter. After the main winch motor establishes magnetic flux, it outputs torque current until the torque current reaches the brake release current value.

[0018] Keep the torque current unchanged. At the same time, the slave PLC issues a brake opening command to control the brake relay to close. After the brake motor is powered on, it controls the brake to open.

[0019] After the brake is completely opened, the slave PLC controls the frequency converter to output an increasing torque current, and controls the main winch motor to start accelerating and running forward, so that the main winch motor quickly obtains a large torque in the belt tightening direction.

[0020] The parking control process includes:

[0021] When the tension detected by the tension sensor received by the slave PLC reaches the set tension value, the slave PLC controls the frequency converter to reduce the torque current. When the torque current drops to the brake closing current value, it remains unchanged.

[0022] After the torque current drops to the brake closing current value, the slave PLC immediately issues a brake command to control the brake relay to disconnect. After the brake motor loses power, it controls the brake to close.

[0023] The slave PLC issues a delay command and waits for the brake to be completely closed.

[0024] After the brake is fully closed, the slave PLC controls the inverter to output a gradually decreasing torque current until it drops to zero, achieving reliable parking.

[0025] When the tension detected by the tension sensor is greater than the upper limit of the set tension value, the slave PLC starts the belt loosening control. The inverter has the same set of parameters in this workflow as in the tension control process. However, when the belt tension is very large, there will be a short-term vehicle slipping phenomenon during the instant of belt loosening. In the open-loop mode of the inverter, the low-frequency band (below 3HZ) cannot ensure full torque output to prevent vehicle slipping. Therefore, in this design, a rotary encoder is added to ensure that the inverter operates in the closed-loop mode, achieving full torque at zero speed to prevent vehicle slipping. The belt loosening control process includes:

[0026] When the slave PLC receives that the tension detected by the tension sensor reaches the upper limit of the set tension value, the slave PLC controls the inverter to reduce the torque current. When the torque current drops to the brake closing current value, it remains unchanged;

[0027] After the torque current drops to the brake closing current value, the slave PLC immediately issues a brake command to control the brake relay to disconnect. After the brake motor loses power, it controls the brake to close;

[0028] The slave PLC issues a delay command and waits for the brake to be fully closed;

[0029] After the brake is fully closed, the slave PLC controls the inverter to output a gradually decreasing torque current until it drops to zero, achieving reliable parking;

[0030] When the parking process ends, the slave PLC controls the operation of the inverter. The slave PLC pre-excites the main winch motor through the inverter by outputting an exciting current in the opposite direction to that in the tension control process. After the main winch motor establishes the magnetic flux, it outputs a torque current until the torque current reaches the brake release current value;

[0031] Keep the torque current unchanged. At the same time, the slave PLC issues an opening brake command to control the brake relay to close. After the brake motor is powered on, it controls the brake to open;

[0032] After the brake is fully opened, the slave PLC controls the inverter to output a gradually decreasing torque current, and controls the main winch motor to start running in low-speed reverse, so that the continuous belt conveyor slowly reduces the tension;

[0033] When the tension value reaches the set tension value, the slave PLC immediately issues a brake command to control the brake relay to disconnect. After the brake motor loses power, it controls the brake to close;

[0034] The slave PLC issues a delay command and waits for the brake to be fully closed;

[0035] After the brake is fully closed, the slave PLC controls the inverter to output a gradually decreasing torque current until it drops to zero, achieving reliable parking.

[0036] The present invention not only has simple control and low cost, but also operates stably and reliably, effectively solving problems such as vehicle slipping, belt breakage, and unstable tensioning existing in the existing belt conveyor tensioning technology. In addition, the present invention can achieve stable adjustment during the tensioning control process, parking control process, and belt loosening control process. However, when the belt tension is very large, there will be a short-term vehicle slipping phenomenon during the instant of belt loosening. In the open-loop mode of the inverter, the low-frequency band (below 3HZ) cannot guarantee full torque output to ensure no vehicle slipping. Therefore, in the present invention, a rotary encoder is added to ensure that the inverter operates in the closed-loop mode, achieving zero-speed full torque to ensure no vehicle slipping. In addition, the process of tightening (loosening) the continuous belt is similar to the lifting (lowering) process of a crane. Combining the control of the brake in the lifting mode of the inverter can achieve completely no vehicle slipping. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 is the control schematic diagram of the present invention;

[0039] Figure 2 is the control flowchart of tightening and loosening the belt of the present invention;

[0040] Figure 3 is the left view structural schematic diagram of the present invention;

[0041] Figure 4 is the top view structural schematic diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0043] Embodiment 1, a reliable automatic tensioning control system for a continuous belt conveyor, as Figure 3 and Figure 4As shown in the figure, it includes a tensioning winch 1. A main winch motor 2 is provided on the tensioning winch 1. A wire rope drum 3 is arranged in transmission cooperation with the main winch motor 2. A speed reducer 11 is arranged between the drive shaft of the main winch motor 2 and the wire rope drum 3. As Figure 1 shown in the figure, a tensioning wire rope 5 that cooperates with the tensioning frame 4 of the continuous belt conveyor is wound on the wire rope drum 3. A tension sensor 6 is arranged on the tensioning wire rope 5. The tension sensor 6 can monitor the tension value of the tensioning wire rope 5 in real time, and the tension state of the tensioning frame 4 can be indirectly known. Both the main winch motor 2 and the tension sensor 6 are connected to the control unit 8. The control unit 8 can, according to the tension value monitored by the tension sensor 6, control the running state of the main winch motor 2 in real time, and then realize the control of the tensioning process, the belt loosening process and the parking process.

[0044] A brake 7 is arranged on the drive shaft of the main winch motor 2. A brake motor 7-1 for driving the opening and closing is arranged on the brake 7. The brake motor 7-1 is connected to the control unit 8 through a brake relay 7-2. The control unit 8 includes a PLC slave station 8-1. Both the tension sensor 6 and the brake relay 7-2 are connected to the PLC slave station 8-1. The PLC slave station 8-1 is connected to a frequency converter 8-2. A resistor box 8-3 is arranged between the main winch motor 2 and the frequency converter 8-2. During the belt loosening operation, the main winch motor 2 will be in a power generation state under the traction of the belt tension. Especially during the final tunneling period when the belt is long, this phenomenon will be more obvious. Therefore, in this embodiment, a resistor box 8-3 matching the frequency converter 8-2 is configured to consume the excessive energy on the bus, and it also plays a certain braking role.

[0045] The main winch motor 2 is connected to the PLC slave station 2-1 through the frequency converter 8-2. The PLC slave station controls the running state of the main winch motor 2 through the frequency converter 8-2. A rotary encoder 8-4 is arranged on the main winch motor 2. The rotary encoder 8-4 is connected to the PLC slave station 8-1. The rotary encoder 8-4 can monitor the speed of the main winch motor 2 in real time, and then transmit the speed signal to the PLC slave station 8-1. The PLC slave station 8-1 controls the frequency converter 8-2 to supply torque current to the main winch motor 2 according to the speed signal, forming a complete closed-loop control system. At the same time, the PLC slave station 8-1 controls the action of the brake relay 7-2 in real time according to the torque current output by the frequency converter 8-2, and then can synchronously control the running state of the brake motor 7-1, that is, can synchronously control the opening and closing of the brake 7 according to the running state of the main winch motor 2.

[0046] During the belt tightening (loosening) process, there is always a large tension, so it is very important to prevent the vehicle from slipping during start-stop. During the operation of the continuous belt conveyor, the main winch motor 2 will be in a low-speed and high-torque state for a long time. Therefore, the frequency converter 8-2 is preferably a heavy-duty frequency converter of the Schneider ATV71 series. This frequency converter can achieve zero-speed full torque in the closed-loop mode, and this feature can greatly reduce the vehicle slipping phenomenon. In addition, the belt tightening (loosening) process of the continuous belt is similar to the lifting (lowering) process of a crane. Combining the control of the brake 7 in the lifting mode of the frequency converter 8-2 can completely prevent vehicle slipping.

[0047] Embodiment 2, a reliable automatic tension control system for a continuous belt conveyor. At least two tension sensors 6 are provided, and each tension sensor 6 is a temperature-compensated tension sensor. Since the tension sensors 6 are under the action of alternating stress for a long time, the probability of failure is increased. Therefore, two sensors are used for redundancy to reduce the probability of equipment shutdown. Since the climates of tunnel construction sites are different, the weather is cold in winter, and the lower temperature will have a greater impact on the tension sensors 6, resulting in a decrease in control accuracy. The use of temperature-compensated tension sensors can ensure the accuracy of the signal output of the tension sensors 6 when the temperature changes greatly. Even after the tension sensor 6 fails, the zero-speed full torque characteristic of the frequency converter 8-2 can be used to periodically judge the current tension value, which can be roughly compared with the tension set value to perform the belt loosening (tightening) action, and then alarm to the upper computer and wait for maintenance.

[0048] The other structures of this embodiment are the same as those of Embodiment 1.

[0049] Embodiment 3, a reliable automatic tension control system for a continuous belt conveyor. The tensioning frame 4 includes a belt turning frame 4-1. A first group of belt turning cylinders 4-2 are arranged on the belt turning frame 4-1. A belt tensioning vehicle 9 is arranged opposite to the belt turning frame. A second group of belt turning cylinders 9-2 corresponding to the first group of belt turning cylinders 4-2 are arranged on the belt tensioning vehicle 9. The belt 10 of the continuous belt conveyor is wound between the first group of belt turning cylinders 4-2 and the second group of belt turning cylinders 9-2. One end of the tensioning steel wire rope 5 is fixed on the belt tensioning vehicle 9. The tensioning steel wire rope 5 can be tensioned and relaxed driven by the main winch motor 2. Furthermore, the tensioning steel wire rope 5 can drive the belt tensioning vehicle 9 to move relative to the belt turning frame 4-1, thereby realizing the tensioning and relaxation of the belt 10.

[0050] The other structures of this embodiment are the same as those of Embodiment 1 or 2.

[0051] Embodiment 4. A reliable automatic tension control system for a continuous belt conveyor. The belt tensioning cart 9 includes a tensioning cart fixed support 9-1. A tensioning cart walking support 9-3 is slidably arranged on the tensioning cart fixed support 9-1. The second group of belt turning cylinders 9-2 are arranged on the tensioning cart walking support 9-3. Driven by the tensioning steel wire rope 5, the tensioning cart walking support 9-3 can move relative to the tensioning cart fixed support 9-1, ensuring the stability of the tensioning and relaxation processes.

[0052] The other structures of this embodiment are the same as those of Embodiment 3.

[0053] Embodiment 5. A reliable automatic tension control system for a continuous belt conveyor. A roller 9-4 is arranged below the tensioning cart walking support 9-3, and a guide rail 9-5 cooperating with the roller 9-4 is arranged above the tensioning cart fixed support 9-1, effectively enhancing the convenience of tensioning and relaxing the belt 10.

[0054] The other structures of this embodiment are the same as those of Embodiment 4.

[0055] Embodiment 6. A reliable automatic tension control system for a continuous belt conveyor. The tensioning winch 1 includes a winch support 1-1 for fixing the main winch motor 2 and a fixed pulley support 1-2 corresponding to the tensioning cart walking frame 9-3. A first fixed pulley group 1-3 is arranged on the fixed pulley support 1-2, and a second fixed pulley group 1-4 corresponding to the first fixed pulley group 1-3 is arranged on the tensioning cart walking support 9-3. The tensioning steel wire rope 5 is wound back and forth between the first fixed pulley group 1-3 and the second fixed pulley group 1-4, and multiple strands of the tensioning steel wire rope 5 are connected in parallel between the first fixed pulley group 1-3 and the second fixed pulley group 1-4, fully ensuring the reliability of traction.

[0056] The other structures of this embodiment are the same as those of Embodiment 4 or 5.

[0057] Embodiment 7. A reliable automatic tension control system for a continuous belt conveyor. A steel wire rope reversing frame 1-5 is arranged between the fixed pulley support 1-2 and the winch support 1-1, and a reversing fixed pulley 1-6 is arranged on the steel wire rope reversing frame 1-5. The tensioning steel wire rope 5 passes through the reversing fixed pulley 1-6 and the first fixed pulley group 1-3 in sequence from the steel wire rope reel 3 and is connected to the second fixed pulley group 1-4, enabling convenient adjustment of the arrangement position of the tensioning steel wire rope 5.

[0058] The other structures of this embodiment are the same as those of Embodiment 6.

[0059] Embodiment 8. A control method for a reliable automatic tension control system of a continuous belt conveyor, as Figure 3As shown, it includes a tension control process, a parking control process, and a loose belt control process. The PLC slave station 8-1 is connected to a control panel 8-5, and the set tension value, brake release current value, and brake closing current value are input into the PLC slave station 8-1 through the control panel 8-5. The tension control process includes:

[0060] When the tension detected by the tension sensor 6 received by the PLC slave station 8-1 is less than the lower limit of the set tension value, the PLC slave station 8-1 controls the frequency converter 8-2 to work. The PLC slave station 8-1 outputs exciting current to pre-excite the main hoist motor 2 through the frequency converter 8-2. After the main hoist motor 2 establishes magnetic flux, it outputs torque current until the torque current reaches the brake release current value;

[0061] Keep the torque current unchanged. At the same time, the PLC slave station 8-1 issues a brake opening command to control the brake relay 7-2 to close. After the brake motor 7-1 is powered on, it controls the brake 7 to open;

[0062] After the brake 7 is completely opened, the PLC slave station 8-1 controls the frequency converter 8-2 to output an increasing torque current, and controls the main hoist motor 2 to start accelerating and rotating forward, so that the main hoist motor 2 quickly obtains a large torque in the tight belt direction.

[0063] The structure of this embodiment can be the same as any one of Embodiments 1-7.

[0064] Embodiment 9, a control method for a reliable automatic tension control system of a continuous belt conveyor. The parking control process includes:

[0065] When the tension detected by the tension sensor 6 received by the PLC slave station 8-1 reaches the set tension value, the PLC slave station 8-1 controls the frequency converter 8-2 to reduce the torque current. When the torque current drops to the brake closing current value, it remains unchanged;

[0066] After the torque current drops to the brake closing current value, the PLC slave station 8-1 immediately issues a brake command to control the brake relay 7-2 to disconnect. After the brake motor 7-1 loses power, it controls the brake 7 to close;

[0067] The PLC slave station 8-1 issues a delay command and waits for the brake 7 to be completely closed;

[0068] When the brake 7 is completely closed, the PLC slave station controls the frequency converter 8-2 to output a gradually decreasing torque current until it drops to zero, realizing reliable parking.

[0069] The structure of this embodiment can be the same as any one of Embodiments 1-7.

[0070] Other control methods of this embodiment are the same as those of Embodiment 8.

[0071] Embodiment 10, a control method for a reliable automatic tension control system of a continuous belt conveyor. When the tension detected by the tension sensor 6 is greater than the upper limit of the set tension value, the PLC slave station 8-1 starts the belt-loosening control. The frequency converter 8-2 has the same set of parameters in this workflow as in the tension control process. However, when the tension of the belt 10 is very large, there will be a short-term vehicle slipping phenomenon during the instant of belt loosening. In the open-loop mode, the frequency converter 8-2 cannot ensure full torque output in the low-frequency band (below 3HZ) to prevent vehicle slipping. Therefore, in this design, a rotary encoder 8-4 is added to ensure that the frequency converter 8-2 operates in the closed-loop mode, achieving full torque at zero speed to prevent vehicle slipping. The belt-loosening control process includes:

[0072] When the PLC slave station 8-1 receives that the tension detected by the tension sensor 6 reaches the upper limit of the set tension value, the PLC slave station 8-1 controls the frequency converter 8-2 to reduce the torque current. When the torque current drops to the brake closing current value, it remains unchanged;

[0073] After the torque current drops to the brake closing current value, the PLC slave station 8-1 immediately issues a brake command to control the brake relay 7-2 to disconnect. After the brake motor 7-1 loses power, the brake 7 is controlled to close;

[0074] The PLC slave station 8-1 issues a delay command and waits for the brake 7 to close completely;

[0075] After the brake 7 closes completely, the PLC slave station 8-1 controls the frequency converter 8-2 to output a gradually decreasing torque current until it drops to zero, achieving reliable parking;

[0076] After the parking process is completed, the PLC slave station 8-1 controls the frequency converter 8-2 to operate. The PLC slave station 8-1 pre-excites the main hoist motor 2 through the frequency converter 8-2 with an exciting current in the opposite direction to that in the tension control process. After the main hoist motor 2 establishes magnetic flux, it outputs torque current until the torque current reaches the brake release current value;

[0077] Keep the torque current unchanged. At the same time, the PLC slave station 8-1 issues an opening command to control the brake relay 7-2 to close. After the brake motor 7-1 is powered on, the brake 7 is controlled to open;

[0078] After the brake 7 is completely opened, the PLC slave station 8-1 controls the frequency converter 8-2 to output a gradually decreasing torque current, and controls the main hoist motor 2 to start running in low-speed reverse, so that the continuous belt conveyor slowly reduces the tension;

[0079] When the tension value reaches the set tension value, the PLC slave station 8-1 immediately issues a brake command to control the brake relay 7-2 to disconnect. After the brake motor 7-1 loses power, the brake 7 is controlled to close;

[0080] The slave PLC 8-1 issues a delay command and waits for the brake 7 to close completely;

[0081] After the brake 7 closes completely, the slave PLC 8-1 controls the frequency converter 8-2 to output a gradually decreasing torque current until it drops to zero, achieving reliable parking.

[0082] The structure of this embodiment can be the same as any one of Embodiments 1-7.

[0083] The other control methods of this embodiment are the same as those of Embodiment 8 or 9.

[0084] The details not elaborated in the present invention are all conventional technical means well known to those skilled in the art.

[0085] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A control method for a reliable automatic tension control system of a continuous belt conveyor, characterized in that: It is used for a roadheader. The system includes a tensioning winch, on which there is a main winch motor. A wire rope drum is arranged in transmission cooperation with the main winch motor. A tensioning wire rope that cooperates with the tensioning frame of the continuous belt conveyor is wound on the wire rope drum. A tension sensor is arranged on the tensioning wire rope. Both the main winch motor and the tension sensor are connected to a control unit. A brake is arranged on the drive shaft of the main winch motor, and a brake motor for driving the opening and closing is arranged on the brake. The brake motor is connected to the control unit through a brake relay. A speed reducer is arranged between the drive shaft of the main winch motor and the wire rope drum. The control unit includes a PLC slave station. The tension sensor and the brake relay are both connected to the PLC slave station. The PLC slave station is connected to a frequency converter. A resistor box is arranged between the main winch motor and the frequency converter. The main winch motor is connected to the PLC slave station through the frequency converter. A rotary encoder is arranged on the main winch motor, and the rotary encoder is connected to the PLC slave station; The rotary encoder monitors the speed of the main winch motor in real time and transmits the speed signal to the PLC slave station. The PLC slave station controls the frequency converter to supply torque current to the main winch motor according to the speed signal. The PLC slave station is connected to a control panel, and a set tension value, a brake release current value, and a brake closing current value are input into the PLC slave station through the control panel; The tensioning frame includes a belt turning frame, on which a first group of belt turning cylinders is arranged. Opposite to the belt turning frame is a belt tensioning vehicle, on which a second group of belt turning cylinders corresponding to the first group of belt turning cylinders is arranged. The belt of the continuous belt conveyor is wound between the first group of belt turning cylinders and the second group of belt turning cylinders. One end of the tensioning wire rope is fixed on the belt tensioning vehicle; The process of this method is as follows; Set the tension value, detect whether the actual tension value is within the range value. If it is, continue to detect. If not, judge the magnitude of the actual tension value and the set tension value; If the actual tension value is greater than the upper limit of the set tension value, loosen the belt and continue to detect; If the actual tension value is less than the lower limit of the set tension value, tighten the belt; This method includes a tensioning control process, a parking control process, and a belt loosening control process; The tensioning control process includes: when the PLC slave station receives that the tension detected by the tension sensor is less than the lower limit value of the set tension value, the PLC slave station controls the frequency converter to work. The PLC slave station outputs exciting current to pre-excite the main winch motor through the frequency converter. After the main winch motor establishes magnetic flux, it outputs torque current until the torque current reaches the brake release current value and keeps the torque current unchanged. At the same time, the PLC slave station issues a brake opening command to control the brake relay to close. After the brake motor is powered on, it controls the brake to open. After the brake is completely opened, the PLC slave station controls the frequency converter to output an increasingly large torque current to control the main winch motor to start accelerating and running forward, so that the main winch motor quickly obtains a large torque in the belt tightening direction; The parking control process includes: when the PLC slave station receives that the tension detected by the tension sensor reaches the set tension value, the PLC slave station controls the frequency converter to reduce the torque current. When the torque current drops to the brake closing current value, it remains unchanged. After the torque current drops to the brake closing current value, the PLC slave station immediately issues a brake command to control the brake relay to disconnect. After the brake motor loses power, the brake is controlled to close. The PLC slave station issues a delay command and waits for the brake to close completely. After the brake closes completely, the PLC slave station controls the frequency converter to output a gradually decreasing torque current until it drops to zero, achieving reliable parking. The belt loosening control process includes: when the PLC slave station receives that the tension detected by the tension sensor reaches the upper limit of the set tension value, the PLC slave station controls the frequency converter to reduce the torque current. When the torque current drops to the brake closing current value, it remains unchanged. After the torque current drops to the brake closing current value, the PLC slave station immediately issues a brake command to control the brake relay to disconnect. After the brake motor loses power, the brake is controlled to close. The PLC slave station issues a delay command and waits for the brake to close completely. After the brake closes completely, the PLC slave station controls the frequency converter to output a gradually decreasing torque current until it drops to zero, achieving reliable parking. After the parking process ends, the PLC slave station controls the frequency converter to work. The PLC slave station pre-excites the main hoist motor of the winch by outputting an exciting current in the opposite direction to that in the tension control process through the frequency converter. After the main hoist motor establishes magnetic flux, it outputs torque current until the torque current reaches the brake release current value and remains unchanged. At the same time, the PLC slave station issues an opening brake command to control the brake relay to close. After the brake motor is powered on, the brake is controlled to open. After the brake is completely opened, the PLC slave station controls the frequency converter to output a gradually decreasing torque current to control the main hoist motor of the winch to start running in low-speed reverse, so that the continuous belt conveyor slowly reduces the tension. When the tension value reaches the set tension value, the PLC slave station immediately issues a brake command to control the brake relay to disconnect. After the brake motor loses power, the brake is controlled to close. The PLC slave station issues a delay command and waits for the brake to close completely. After the brake closes completely, the PLC slave station controls the frequency converter to output a gradually decreasing torque current until it drops to zero, achieving reliable parking.

2. The control method of the reliable continuous belt conveyor automatic tension control system according to claim 1, characterized in that: At least two tension sensors are provided, and each tension sensor is a temperature-compensated tension sensor.

3. The control method of the reliable continuous belt conveyor automatic tension control system according to claim 2, characterized in that: The belt tensioning vehicle includes a tensioning vehicle fixed support, and a tensioning vehicle walking bracket is slidably arranged on the tensioning vehicle fixed support. The second group of belt turning cylinders is arranged on the tensioning vehicle walking bracket.

4. The control method of the reliable continuous belt conveyor automatic tension control system according to claim 3, characterized in that: Rollers are arranged below the tensioning vehicle walking bracket, and a guide rail matched with the rollers is arranged above the tensioning vehicle fixed support.

5. The control method of the reliable continuous belt conveyor automatic tension control system according to claim 4, characterized in that: The tensioning winch includes a winch bracket for fixing the main hoist motor and a fixed pulley bracket corresponding to the tensioning vehicle walking frame. A first fixed pulley group is arranged on the fixed pulley bracket, and a second fixed pulley group corresponding to the first fixed pulley group is arranged on the tensioning vehicle walking bracket. The tensioning steel wire rope is wound back and forth between the first fixed pulley group and the second fixed pulley group, and multiple strands of the tensioning steel wire rope are connected in parallel between the first fixed pulley group and the second fixed pulley group.

6. The control method of the reliable continuous belt conveyor automatic tension control system according to claim 5, characterized in that: A wire rope reversing frame is arranged between the fixed pulley bracket and the winch bracket. A reversing fixed pulley is arranged on the wire rope reversing frame. The tensioning wire rope sequentially passes through the reversing fixed pulley and the first fixed pulley set from the wire rope reel and is connected to the second fixed pulley set.

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